Add the sql concat function to query builder

modules/store/src/main/scala/docspell/store/qb/DBFunction.scala

@@ -1,5 +1,7 @@
 package docspell.store.qb
 
+import cats.data.NonEmptyList
+
 sealed trait DBFunction {}
 
 object DBFunction {
@@ -31,6 +33,8 @@ object DBFunction {
 
   case class Sum(expr: SelectExpr) extends DBFunction
 
+  case class Concat(exprs: NonEmptyList[SelectExpr]) extends DBFunction
+
   sealed trait Operator
   object Operator {
     case object Plus  extends Operator

modules/store/src/main/scala/docspell/store/qb/DSL.scala

@@ -98,6 +98,9 @@ trait DSL extends DoobieMeta {
   def substring(expr: SelectExpr, start: Int, length: Int): DBFunction =
     DBFunction.Substring(expr, start, length)
 
+  def concat(expr: SelectExpr, exprs: SelectExpr*): DBFunction =
+    DBFunction.Concat(Nel.of(expr, exprs: _*))
+
   def lit[A](value: A)(implicit P: Put[A]): SelectExpr.SelectLit[A] =
     SelectExpr.SelectLit(value, None)
 

modules/store/src/main/scala/docspell/store/qb/impl/DBFunctionBuilder.scala

@@ -32,6 +32,10 @@ object DBFunctionBuilder extends CommonBuilder {
       case DBFunction.Substring(expr, start, len) =>
         sql"SUBSTRING(" ++ SelectExprBuilder.build(expr) ++ fr" FROM $start FOR $len)"
 
+      case DBFunction.Concat(exprs) =>
+        val inner = exprs.map(SelectExprBuilder.build).toList.reduce(_ ++ comma ++ _)
+        sql"CONCAT(" ++ inner ++ sql")"
+
       case DBFunction.Calc(op, left, right) =>
         SelectExprBuilder.build(left) ++
           buildOperator(op) ++